From Susceptibility to Severity: The Impact of Interleukin-33 rs1929992 Polymorphism on Asthma in a Taiwanese Population

Asthma is a chronic inflammatory airway disease strongly influenced by genetic factors. Interleukin-33 (IL-33), a key mediator of type 2 immune responses, has been implicated in airway inflammation and remodeling. However, the effects of IL-33 polymorphisms on asthma susceptibility and severity remain unclear, particularly in East Asian populations. This study investigated five IL-33 polymorphisms (rs1891385, rs16924159, rs12551256, rs1929992, and rs7044343) in relation to asthma risk and severity in Taiwanese individuals. A total of 198 asthmatic patients and 453 age- and sex-matched controls were enrolled. Genotypes were determined using PCR-RFLP. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess associations with asthma susceptibility and severity. Among the five polymorphisms, only rs1929992 was significantly associated with asthma. Compared with the TT genotype, CT and CC carriers had reduced asthma risk (OR = 0.61 and 0.51, respectively). The dominant model (CT+CC) also showed a protective effect (OR = 0.58, 95%CI = 0.40–0.82, p = 0.0032), which was supported by allelic analysis (OR = 0.70, 95%CI = 0.55–0.89, p = 0.0044). Among the five polymorphisms, rs1929992 was associated with asthma susceptibility. Under the dominant model, CT + CC carriers showed lower odds of asthma than TT carriers (OR = 0.58, 95% CI = 0.40–0.82, p = 0.0032), and the association remained significant after correction for multiple testing. Exploratory stratified analyses identified associations in the younger and male subgroups, while exploratory severity analysis suggested lower odds of more severe asthma among variant genotype carriers. These secondary findings should be considered hypothesis-generating because of the reduced subgroup sample sizes. Overall, rs1929992 was associated with asthma susceptibility in this Taiwanese population; however, independent replication and functional studies are required before its biological or clinical relevance can be established.